In many applications of imaging X-rays are used to examine and analyze the structure and material properties of multiple objects like human bodies, organs, tissues or crystal structures. One of the basic areas of health care in which X-radiation is used is radiography. Radiography may be used for fast, highly penetrating images in particular for regions with a high bone content. Some forms of radiography use are panoramic X-rays, mammography, tomography and radiotherapy.
For computed tomography (CT) for example, patients are illuminated by beforehand generated X-rays from various positions and angles, in order to reconstruct a three dimensional (3D) model of the analyzed anatomical structure. Using for example a CT, the object of interest may be exposed to the radiation from 360 degrees and a model of the object of interest may be computed from so called projection images. As a time deviation between the origins of the different pictures is unavoidable for moving objects, motion artifacts of the reconstructed model are still a challenging task.
Conventional X-ray sources are heated cathode filaments which thermally emit electrons. The electrons are accelerated as a beam and then strike a target material, where subsequently X-rays are generated. The point where the electron beam strikes the angled target or anode is called the focal spot. Most of the kinetic energy contained in the electron beam is converted into heat, but a certain amount of the energy is converted into X-ray photons. At the focal spot, X-ray photons are emitted. Thereby a heating up of the electron absorbing target up to the melting point of the used material often limits the intensity of the generated X-ray beam of known X-ray sources.